For self-evident reasons, distribution networks are stationary installations and this is reflected by the manner in which electric energy has been charged. Thus, groups of tap-off facilities in the form of socket means and/or stationary installations, for instance in a house property or a flat, have been connected to the distribution network via an electricity meter, and for each electricity meter a physical or juristical person has been liable for payment. Concurrently with an increased use of electric appliances and machinery and the continued development of electrically driven vehicles, the individual users will in future have an increased need of using electric energy also outside the place where they live and their place of work. For instance, there will be a great demand for "filling stations" for electric cars.
By using a differentiated charging system, in which an individual user pays for the electric energy consumed, independently of the geographic point at which the consumption takes place, it would, for example, be possible to arrange tap-off facilities in conjunction with parking places and the like, such that the person at the time using a parking place can use the time of stoppage to recharge the batteries of the car and/or heat the passenger compartment before starting in a cold climate or in cold weather, or cooling the compartment in a warm climate. Customers in such a power-charging system would probably be prepared to pay a higher price of energy for increased accessibility of electric energy.
It is known to communicate from a central computer with individual electricity meters via signals superimposed on the distribution network, thereby obtaining additional functions and supplying the customers with additional services. For instance, it is possible to accomplish, by such a system, the reading of individual electricity meters directly from the central computer, or to provide electricity meters with card readers, as disclosed in e.g. GB 2,107,093, thereby facilitating the charging of consumed electric energy. By means of push buttons in the electricity meter cupboard it is also possible for the user to communicate with the central computer and, for instance, request activation of an external current circuit, such as request from the house or flat switching-on of electric heating in a weekend cottage or the like. Such a system implies, however, merely that an individual electricity meter is identifiable and that the person liable for payment of the electricity meter is charged with the consumed electric energy. Thus, charging is still effected in respect of a fixed geographic point.
SE 9202514-7 discloses the controlling of a group of tap-off facilities, which are arranged e.g. at a parking place or a caravan site, from a control board. In such an establishment, the user is obliged to walk to the control board, identify himself by means of a charge card or the like and, via a set of buttons, select which tap-off facility/facilities he wishes to use and pay the electricity charges therefor. Communication between the control board and the respective tap-off facilities is intended to occur via radio signals or data circuits especially arranged for the purpose. By the user being obliged to be present at the control board for identification and selection of tap-off facilities, such establishments must, of course, be restricted to a small area. Moreover, the user will obtain but little safety, since his plug can easily be removed by an unauthorised person who may then put his own plug into the socket and so "steal" electric current which the rightful user will have to pay.
SE 9202823-2 discloses a recharging device for recharging the energy storage units of an electric vehicle. The only purpose of this recharging device is to reduce the load on the distribution network and to serve as an adaptation circuit to permit recharge of the vehicle with electric current having a varying number of phases and varying voltages and frequencies. The device may also comprise a transmitter and a receiver for communication via the distribution network.
SE 425,123 discloses a plant for central and automatic reading, registration and control of energy consumption meters mounted at the consumer's premises. An individual electricity meter communicates with the power distributor via signals superimposed on the distribution network. The purpose is to provide a plant having better means for optimum utilisation of the electric energy at its cheapest. Charging thus occurs in respect of a fixed geographic point.
U.S. Pat. No. 4,352,992 discloses a load management system in which load controllers selectively connect and disconnect high power deferrable loads on the distribution network in order to permit levelling of periods of peak load demand. The communication between the power distributor and the power consumer occurs via radio signals. Charging occurs in respect of a fixed geographic point.
EP 0 047 089 concerns an apparatus and a method for connecting and disconnecting power-consuming units to and from the distribution network in a predetermined priority order for the purpose of permitting automatic disconnection of current during periods of peak load demand and, thus, at a high price of energy. Like before, charging occurs in respect of a fixed geographic point.